The email contains the username and password credentials. If the users do not sign in to dashboard with the new password, the organization will not be linked to the new organization admin email.
For example, if these new users are organization admins on several other organizations and they are also added to a new organization but they do not sign in to dashboard with the new password but instead they sign in with their old password, then the users will not be able to see the new added organization under their dashboard accounts.
The passwords need to be synced together. When the new organization admins sign in with the new password, they are prompted to create a new password. Once created, the next time the organization admins sign into the Meraki Dashboard they will see the new organization listed under their accounts.
If for some reason the new added organization admins are unable to receive the email with the username and password credential from Meraki, simply use the password reset link at dashboard.meraki.com to sync the passwords.
If you still do not receive the password reset email from Meraki, check your spam folder. Otherwise, please contact Cisco Meraki Support.